BOSTON - A review of 15 years of patient records by researchers at the Duke Comprehensive Cancer Center indicates that children who develop medulloblastoma, a common childhood brain cancer, were more likely to have been born in late summer or fall than the average U.S. population.
If environmental factors that vary seasonally, such as water pollutants, could be identified and examined for their effects on brain development in the womb, this finding may eventually help clarify some causes of these tumors, suggested Dr. Edward Halperin, leader of the study and chair of radiation oncology at Duke University Medical Center.
"Children born in the fall would have been conceived the previous winter, and their brains would develop during the spring," explained Halperin. "What is happening during the spring more than at other times of the year that could explain this difference? Given other researchers' similar results, it's worth doing more research."
The Duke researchers prepared the findings for presentation Sunday at the annual meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO). The study was funded by a special cancer grant from the Ladies' Auxiliary of the Veterans of Foreign Wars of North Carolina.
In addition to this study, which included only patients treated at Duke primarily between 1983 and 1999, studies from Japan and Norway have demonstrated a similar imbalance in birth date distribution among medulloblastoma patients compared to the population at large. While births in general are not uniformly distributed throughout the year, for each of these studies the peak for patients exceeded that of the general population of the country, said Halperin.
Because there are so few cases of childhood cancer each year in the United States - about 8,000 - the number of new cases of medulloblastoma is quite small, and minuscule compared to cancer in adults. As a result of the small patient pool, Halperin said that a population-based study would be helpful to see if the link with birth date holds for patients across the United States.
In the study of 122 medulloblastoma patients at Duke, Halperin and his colleagues, Stephen George and statistician Dorothy Watson, also examined links between gender, age, duration of symptoms before diagnosis, and stage of disease at diagnosis.
Among other findings, the analysis showed that boys were significantly more likely to have symptoms for a longer period of time before medulloblastoma is diagnosed.
"The link between gender and duration of symptoms may be due to gender expectations affecting when we take boys or girls to the doctor," Halperin said. "For example, if a boy walks into a room, stumbles and knocks over a vase, the clumsiness may be brushed aside because he's a boy. There may be an overwhelming societal bias of behavior expectations for girls and boys that affects when clumsiness and other symptoms of medulloblastoma are considered to be 'symptoms' rather than normal behavior."
To pursue this hypothesis, it could be interesting to examine possible gender expectation effects for other cancers or diseases with behavioral symptoms, Halperin said.
Gender was not associated with stage of disease, but instead, for boys and girls, the longer the duration of symptoms, the lower the stage of disease at diagnosis. While this seems counterintuitive because usually in cancer, the "later" the diagnosis, the higher the stage of disease, this finding is not without precedent, doctors said.
"We're all taught that an early diagnosis is the key to a cure when it comes to cancer, and that it follows that early diagnosis must mean quickly diagnosed," said Halperin. "However, with brain stem glioma, we've shown that a shorter duration of symptoms before diagnosis is related to a worse prognosis. With this study, we show that medulloblastoma behaves similarly.
"A possible explanation could be what is called 'cerebral plasticity' - the idea that when tumors grow slowly in the brain, the brain can adapt, creating new pathways to accomplish the affected functions," he continued. "When they grow quickly, perhaps the brain cannot adapt, leading to a more rapid escalation of symptoms."
Although additional research is needed, Halperin said these findings could affect lawsuits claiming delayed diagnosis, as well as guidelines for obtaining CT scans for symptomatic children, and insurance for covering these scans.
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